The expression “disk device” herein denotes a portable device including at least one disk drive. Examples of disk devices are media players, notebook computers, tablet PCs, PDAs (personal digital assistants), smart cellular phones (e.g., phones capable of playing and displaying multimedia content), and portable computing systems, each including at least one disk drive.
Disk drives of disk devices are prone to damage and data skipping when subjected to physical impacts. A typical impact scenario is an accidental drop of a disk device. An impact can corrupt data that are being or have been read from a disk drive (or data that are being or have been written to the drive) and/or can damage the disk drive itself. It would be desirable to predict physical impact to which a disk device will likely be subjected, so that each data reading head (of each disk drive of the device) can be quickly placed into a “parked” position, or so that other action can quickly be taken to protect each disk drive from physical damage if and when the impact occurs.
It has been proposed to include an accelerometer in a portable computer or other portable device (e.g., a portable media player, PDA, or MP3 digital audio player) for use in protecting the portable device (e.g., to protect a disk drive thereof by performing a disk drive head parking operation), for example, to take protective action when acceleration data from the accelerometer indicate that the device will suffer imminent impact or that the device's acceleration is within a predetermined range (e.g., a predetermined range including gravitational acceleration, g=9.8 m/sec2). For example, U.S. Reissue Pat. 35,269, to Comerford, describes a dedicated processor (installed in a portable computer) that monitors the output of an accelerometer (also installed in the computer). When the sensed acceleration is within a predetermined range near gravitational acceleration, the dedicated processor issues an interrupt to the computer's CPU to trigger a head parking operation, or itself triggers parking of the disk drive heads and optionally also braking of the motion of each disk.
Similarly, U.S. Pat. No. 6,520,013 and U.S. Pat. No. 6,768,066, to Wehrenberg, describe parking a read/write head of a data storage device (in a processing system) in response to sensing that the processing system's acceleration has reached a threshold value.
Also similarly, U.S. Pat. No. 5,835,298, issued to Edgerton, et al., describes a dedicated processor (installed in a portable computing device) that monitors the output of an accelerometer (also installed in the computing device), processes the accelerometer data (e.g., by performing numerical integration thereon) to generate data indicative of translational velocity (or the square, or other function, of the translational velocity) of the computing device, and, when the translational velocity (or the square thereof) exceeds a predetermined threshold, takes steps to protect a disk drive of the device (e.g., by initiating an operation to park the disk drive heads).
U.S. Pat. No. 6,101,062, to Jen, et al., discloses a feedback loop in which a processor (servo processor 102) controls motor speed of a disk drive in response to measured motor spin current data (indicative of motor speed of the disk drive), processes the measured data to infer whether the disk drive is undergoing hazardous acceleration, and initiates protective action (e.g., triggers parking of disk drive heads, or powers down the disk drive) in response to inferring that hazardous acceleration is occurring. However, the data processing (to infer that hazardous acceleration is occurring) requires complicated exponential averaging of the data (by generating a long decay exponential average and a short decay exponential average of the data and comparing the two averages), or the complicated steps of obtaining and storing a library of motion signatures (indicative of hazardous acceleration), comparing the measured data to the stored motion signatures, and inferring that hazardous acceleration is occurring when the measured data match a stored motion signature.
It has also been proposed to include an accelerometer in a digital camera, and use acceleration data from the accelerometer to prevent picture blurring in image data generated by the camera, or to switch between operating modes (e.g., landscape and portrait modes) when taking still pictures or shooting video.